The Program on Surgical Control of the Hyperlipidemias (POSCH) is a secondary (post a single myocardial infarction, unifactorial (hypertension, diabetes, and other major risk factors excluded) atherosclerosis-lipid intervention trial. The core facilities of POSCH (Central Lipid Laboratory, Central Electrocardiography Laboratory, Central Arteriography/ Radiology Laboratory, and the Office of Programs Administration) are located at the University of Minnesota; the four clinical centers of POSCH are at the University of Minnesota, University of Arkansas, University of Southern California, and the Lankenau Research Center, Philadelphia. The mode of intervention for POSCH is the partial ileal bypass operation. POSCH data have documented that this procedure causes a 25% reduction in total plasma cholesterol, a 40% LDL-cholesterol lowering, an 8% increase in the HDL-cholesterol, and an 80% increase in the HDL/LDL ratio. In addition to clinical endpoints, this trial provides sequential analyses of coronary arteriograms for at least five years after randomization for each participant. Recruitment and screening terminated in 1982-1983, and randomization terminated July 19, 1983 with 838 participating subjects. POSCH is currently in its follow-up phase. This application is for the completion of follow-up, termination of the trial, and analysis and publication of data. The results of this trial will answer the questiion of whether total plasma cholesterol reduction, or more precisely the lowering of the LDL-cholesterol and the raising of the HDL-cholesterol fractions, will affect the atherosclerosis process after a myocardial infarction.